1. Introduction to Digital Audio

2. Essential Question:
How does understanding time based media effectively enhance the multimedia process?

3. Introduction to Sound
Sounds are vibrations that travel though the air or some other medium
A sound wave is an audible vibration that travels through air or water.
The loudness or intensity of a sound is measured in Decibels (dB).
The frequency of a sound is measured in Hertz (Hz) Hertz=Kilohertz (kHz)

4. The Range of Human Hearing
20 Hz to Hz (20 kHz
Normal Conversation – 1 kHz to 4 kHz
Dogs can hear up to 35 kHz (ultrasound)
Sounds below 20 Hz are infra sounds (earthquakes)

5. Anatomy of a Sound Wave
Crest: Point that exhibits maximum amount of upward displacement from the rest position.
Trough: Point that exhibits maximum amount of downward displacement from the rest position.
Wavelength: Distance from crest to crest.
Amplitude: Distance from rest to crest or rest to trough.
Frequency: Number of waves to pass a point in one second. (How Fast)
Pitch: Quality of a sound determined by the rate of vibration. The degree of highness or lowness of a tone. (How High)

6. AMPLITUDE
FREQUENCY
PITCH

7. Click on the image to visit: inknowthat.com to view a sound animation

8. Converting Analog Sound to Digital Sound
Analog sound is a continuous phenomena, such as speaking or an electrical pulse from an instrument.
Computers can only deal with discrete information, so analog sound must be converted to digital, which is called sampling.
Sampling converts electrical energy to binary code (1’s and 0’s) that is readable by computers.
Click to View Sampling Animation

9. Sampling (Continued)
Sample Rate: The rate or frequency at which a sound is sampled to digitize it. Measurements of a sound wave over time measured in Hz (cycles/sec).
48 kHz: standard for digital audio
CD audio is sampled at 44.1 kHz
Bit Rate (Depth): the number of computer bits that are conveyed or processed per unit of time.
Normally expressed in kilobits per second (kbps).
A higher bit means generally means better quality (resolution).
16 bit: 65,536
24 bit: 16,777,216
Digital Audio Bit Depth, Sampling Rate, Interpolation

10. Audio Software Terms
Waveform: a visual representation of an audio signal.
Clip: is a short segment of audio. It can be combined with others to make an audio track.
Track (Channel): an area upon which audio moves. It may be a single waveform or could be made up of clips.

11. Audio Software Terms (Continued)
Channel
Single Channel=Mono
Two Channels=Stereo
reproduction of sound using two or more independent audio channels in a way that creates the impression of sound heard from various directions, as in natural hearing.
Trim: removes everything from the left and right of selected audio.
Amplify: change the volume of selected audio.

12. Exporting Files
Exporting: the process of saving an audio file in a format other than the format of the program it was created in.
Common Audio Formats
WAV (.wav)
Developed by IBM and Microsoft for Windows
High Quality (Lossless)
Large File Size
AIFF
Developed by Apple
MP3 (.mp3)
Compressed format
Popular for music (MP3 Players)
Well suited for Internet
Ogg Vorbis (.ogg)
Open Source
Well Suited for Internet
Popular with Gaming Industry

13. AUP Audio File
An AUP file is the native file format for Audacity. An AUP can be opened only in Audacity where the original content can be edited.
When you use the Save or Save As command in Audacity, it saves the file in the .aup format. The export command is used to convert an Audacity file to a .wav, .mp3, .aiff, or.ogg.

14. Question:
A group of NTHS students are analyzing audio files to identify short segments to be included in a photo montage for the year-end picnic. These segments are examples of:
Waveforms
Clips
Track
Channels
Answer: B

15. Question:
Margie has compiled a collection of funniest moments from her weekly radio show and wants to share them on her website. Which file formats are best suited for use on the internet?
WAV or AIFF
AIFF or OGG
WAV or MP4
OGG or MP3
Answer: OGG or MP3

16. In figure 3.01B, if the soundwave represents one second of time, what is the frequency?
NCCTE.9_12.BE.BD RBT: 2 4 5 10
Question:
Answer: C
In figure 3.01B, if the soundwave represents one second of time, what is the frequency?
A. 2
B. 4
C. 5
D. 10

17. Question:
Which sound characteristic would be most represented by a bull frog croaking?
crest
trough
pitch
wavelength
Answer: Pitch

18. Question:
The mix master is using the visual representation of different sound clips to determine where they are most effectvely combined. These visuals are examples of :
Waveforms
Clips
Storyboarding
Channels
Answer: Waveforms

19. Question:
Christopher has finished a presentation on music history and wants to include the highest quality the music samples. Which file type would be most appropriate? 
WAV or AIFF
AIFF or OGG
WAV or MP3
OGG or MP3
Answer: WAV or AIFF

20. What have you learned? What is soundwaves?
What is the range for human hearing? For dogs?
What is a crest? Trough? Wavelength? Frequency? Amplitude? Pitch
What is sample rate? Bit rate?
What is waveform? Clip? Track? Channel? Trim? Amplify?
What are common audio formats? Why is each used?

21. Assignment:
3.01 Sound Basics Worksheet and Determine File Types

22. Class Assignment:
Learning Audacity
Piano Movers

23. Assignment: A Wild Night in Kansas
Check microphone & headphones before starting
Can move so you are not next to someone
Do both audio and sound effects. Search internet for free sound effects.
Save as AUP file first. Export as Mp3.
Turn in on Canvas when completed as MP3

24. Assignment: A Night in the Graveyard
Check microphone & headphones before starting
Can move so you are not next to someone
Do both audio and sound effects as MP3.
Today: Add effects from Audacity. Example: Fade In/Out, etc.
Save as aup file first. Export as Mp3.
Turn in on Canvas when completed as MP3

25. Assignment: Create a Radio Promotion Requirements:
Choose a worthy cause, business, club or sport that you can promote
Thursday: Must plan what you will say and have it typed or written (50 Points – must be turned in)
Friday: Put Together Promotion
Audio length: 90 Seconds (20 Points)
Promotion must have good flow, sound effects, effects, etc. (30 Points)